Method and system for identity verification using multiple simultaneously scanned biometric images

ABSTRACT

Accuracy and speed of biometric identity verification are significantly improved by use of multiple simultaneous scans of biometric features of a user, such as multiple fingerprints, using multiple scanners ( 40, 50 ) of smaller size than would be needed to accommodate all of the fingerprints in a single scanner ( 30 ), and using multiple parallel processors ( 42, 52 ), or a single higher speed processor, to process the fingerprint data more efficiently. Obtaining biometric data from multiple user features by use of multiple scanners increases verification accuracy, but without the higher cost and slower processing speed that would be incurred if a single large scanner were to be used for improved accuracy.

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to identity verificationtechniques using biometric data and, more specifically, to the use ofbiometric data, such as fingerprints, to provide identity verificationin real time. Although techniques for biometric verification of personalidentity have been widely disclosed, widespread application of biometricidentity verification systems to consumers has not occurred, largelybecause of the relatively high cost and lack of practical usability ofsuch systems for high-speed or real-time identity verification. To beusable in a practical application, a biometric verification system mustmeet requirements of accuracy, size and convenience. “Accuracy” pertainsprincipally to the percentage of access requests that are granted tolegitimate users on a first attempt. “Size” refers to the size ofscanning and verification equipment, and particularly the size of thefingerprint scanner. As will be further discussed, the scanner size hasan impact on cost, speed of operation, and convenience for the user.“Convenience” includes ease of use as well as speed of operation. Afingerprint scanner may be easy to use, but a long processing delay willreduce its overall convenience. Low accuracy also negatively impactsconvenience of use.

[0002] Devices using fingerprint scanning of a single finger, witheither rolled or flat scanning, have a single trial accuracy limit of95-99% using any currently known fingerprint matching algorithm. Thus,between one and five of every one hundred attempts at identityverification by legitimate users will result in failure to gain accessto whatever is being protected by the biometric device. Upon rejection,the user must make another attempt, possibly using an alternate fingerif the system has been set up to accommodate this type of action. Inmany important applications of biometric verification, this level ofaccuracy is not acceptable from a convenience standpoint.

[0003] Although accuracy can be improved by increasing the size of thefingerprint scanner to accommodate a larger area of the finger, orpossibly two fingers, there is an important tradeoff that designers ofsuch systems face. Larger scanning devices cost significantly more andrequire a significantly longer processing time. In fact the cost of afingerprint scanner increases at greater than a linear rate. That is tosay, the cost of one large sensor will be significantly greater than thecombined cost of two sensors of half the size of the large sensor. Theprocessing time for virtually all verification algorithms is roughlyproportional to the square of the sensor size. Accordingly, improvementsin accuracy obtained by using a larger fingerprint sensor areaccompanied by both a higher sensor cost and a longer processing time.In other words, accuracy is improved only at the expense of economy andconvenience.

[0004] All commercially available fingerprint identity verificationsystems available at the time of the present invention utilize singlefinger collection and verification, with two possible exceptions. Botharise in law enforcement applications, where real-time identityverification is rarely a concern. Some police agencies use a singlefingerprint capture device to capture images of all ten fingers insuccession. The images are not captured simultaneously and the purposeis not to support real-time verification of identity. Police may alsouse a large fingerprint scanner to simultaneously record thefingerprints of all four fingers on each hand, referred to as a “slap.”The purpose of a slap, on a conventional (ink-on-paper) fingerprintcard, is to verify that each fingerprint image has been placed in thecorrect box on the card. When a “slap” is obtained with a scanner, thepurpose is the same, i.e., to verify that the correct fingers have beenused to obtain of each of four separately scanned fingerprints. A verylarge and expensive scanning device is used to obtain the “slap.”

[0005] It will be apparent from the foregoing that there is a need foralternative technique or improving the accuracy and convenience offingerprint identity verification systems. The present invention isdirected to this end.

SUMMARY OF THE INVENTION

[0006] The present invention resides in a method and correspondingsystem, for obtaining increased accuracy in identity verification byusing multiple simultaneously scanned biometric features. Briefly, andin general terms, the method of the invention comprises the steps of:scanning at least two biometric features of a user simultaneously, usingat least two practically identical biometric scanners; processing datafrom the at least two scanners in at least one processor, to obtainbiometric data that uniquely identify the scanned biometric features;and comparing the biometric data with reference biometric data recordedfrom the user during an enrollment procedure, to verify the identity ofthe user. Simultaneous use of multiple biometric scanners and multipleparallel processors, or a single higher speed processor, providesdesirable improvements in accuracy and processing speed, at asignificantly lower cost than by using a single, larger biometricscanner.

[0007] In the disclosed embodiment of the invention, the step ofscanning includes scanning at least two fingerprints of the usersimultaneously. The scanning step can be either scanning thefingerprints with at least two two-dimensional scanners, or scanning thefingerprints with at least two one-dimensional scanners. Ifone-dimensional scanners are used, the step of processing the data fromthe scanners includes converting one-dimensional scanner data totwo-dimensional fingerprint data.

[0008] In terms of a novel system, the invention comprises: at least twopractically identical biometric scanners, for scanning at least twobiometric features of a user simultaneously; at least one processor, forprocessing data from the at least two scanners to obtain biometric datathat uniquely identify the scanned biometric features; and comparisonlogic, for comparing the biometric data with reference biometric datarecorded from the user during an enrollment procedure, to verify theidentity of the user. Simultaneous use of multiple biometric scannersprovides desirable improvements in accuracy and processing speed, at alower cost than by using a single, larger biometric scanner.

[0009] In the system as disclosed by way of example, the scanners arefingerprint scanners, for scanning at least two fingerprints of the usersimultaneously, and parallel processors are used. It will be understood,however, that a single processor operating at a higher speed couldhandle the processing of data from multiple scanners. The fingerprintscanners may be two-dimensional scanners or one-dimensional scanners. Ifone-dimensional scanners are used, the parallel processors each includeconversion logic, for converting one-dimensional scanner data totwo-dimensional fingerprint data. In one disclosed embodiment, theone-dimensional scanners are combined to form a single, logicallysegmented one-dimensional scanner.

[0010] It will be appreciated from this summary that the presentinvention provides significant advantages over identity verificationsystems available in the past. In particular, the invention improvesaccuracy because of its simultaneous use of multiple biometric features,but without the sacrifices of higher cost and slower speed usuallyassociated with increasing the scope of a biometric scan. Other aspectsand advantages of the invention will become apparent from the followingmore detailed description, take in conjunction with the drawings, ofwhich the following is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a simplified block diagram showing the basic functionsof a fingerprint identity verification system;

[0012]FIG. 2 is diagrammatic view of a single two-dimensionalfingerprint sensor of the prior art, wherein accuracy improvement isobtained at the expense of a more costly sensor and slower processingspeed;

[0013]FIG. 3 is a diagrammatic view of a pair of two-dimensionalfingerprint sensors used in accordance with the present invention, forhigher accuracy without high cost or slow processing speed;

[0014]FIG. 4 is a diagrammatic view of a pair of one-dimensionalfingerprint sensors used in accordance with the present invention; and

[0015]FIG. 5 is a diagrammatic view of a single one-dimensional sensorused in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] As shown in the drawings for purposes of illustration, thepresent invention pertains to identity verification using biometricdata, such as fingerprints. In a typical system of this general type, auser is first “enrolled” by use of an enrollment fingerprint sensor, asshown at reference numeral 10. The fingerprint is analyzed, as indicatedin block 12, to generate a set of parameters that uniquely define thefingerprint in some manner. The specific steps performed in analysis ofthe “reference” fingerprint will depend on which fingerprint comparisonalgorithm is to be used to identify the user. In general, thefingerprint image will be analyzed to identify a number features thatuniquely define the fingerprint. In many algorithms, it is the presenceand relative positions of fingerprint features that are used to uniquelyidentify the fingerprint. For most practical systems, recording anentire fingerprint image would exceed the capacity of any economicaldatabase and would result in very slow comparison times. Therefore, mostsystems record only the salient features of the reference fingerprintimage. As part of the enrollment process, the user also provides someindependently verifiable form of identification, as indicated by block14. A unique user identifier, such as an employee number of customernumber, is stored with the reference fingerprint data in a userfingerprint database, shown as block 16.

[0017] In using this system for identity verification, a user places afinger over a fingerprint sensor 18, from which is derived a digitizedimage of the user's fingerprint. The user also supplies a useridentification, such as an employee number or customer number, using anidentification input device 20 of some kind. This could be a keypad orbadge or card reader, for example. The fingerprint image is analyzed, asshown in block 22, in the same way that the reference fingerprint imagewas analyzed, and the resulting parameters are compared with those of areference fingerprint image retrieved from the database 16, using theuser's identification to access the database. If the currently obtainedfingerprint image matches the reference image, the user is grantedaccess to a property being protected by the system, as indicated by the“pass” signal on line 26 from the comparison logic 24. If the comparisonresults in a failure to verify the user's identity, the attempted accessis rejected, as indicated by the “reject” signal on line 28. Theprotected property may be a physical building or vehicle, or it may be acomputer system, providing access to a bank account, for example.

[0018] Unfortunately, identity verification using a single fingerprintwill correctly identify a legitimate user only approximately 95-99% ofthe time. Although this level of accuracy can be improved by increasingthe size of the sensor 30 to accommodate the combined width of twofingers 32 that are pressed against the sensor, as showndiagrammatically in FIG. 2, doing so results in a significantly higherequipment cost and a significantly longer processing time for eachfingerprint comparison.

[0019] In accordance with the present invention, two or morefingerprints are captured using multiple small, inexpensive sensors 40(FIG. 3). Each of the fingers 32 is pressed against one of the sensors40, and each sensor provides its output data to a separate processor 42.The processors 42 operate in parallel. Since information is beingcollected from more than one finger, a smaller sensor size can be usedfor each finger, thereby reducing the cost of the sensors and theprocessing time for each processor 42. Even though the cost andprocessing time have been lowered, a significant improvement in accuracycan be achieved. For example, if it is assumed that a relatively smallsensor size is used, providing a single-finger accuracy of 95%, thencollecting two fingerprints simultaneously would support accuracy ashigh as (1.0−(.05×.05))=99.75%, assuming completely independent resultsfor the two fingers. The degree of independence between the fingerprintsof two fingers has been measured empirically, and although not complete,it is very close to complete. In the above example, the degree ofindependence would support an accuracy of approximately 99.6%.

[0020] The data obtained from a two-dimensional fingerprint sensor canalso be obtained from a one-dimensional sensor, across which the fingeris “swiped.” Therefore, another variant of the invention is to apply thesame principles to a pair of one-dimensional sensors 50, as shown inFIG. 4. The fingers 32 are swiped across the respective sensors 50, theoutputs of which are coupled to separate, parallel processors 52.Moreover, because one-dimensional sensors do not generally increase incost as the square of the size, the concept of the invention can beapplied to a slightly wider sensor 60 that allows the multiple fingers32 to be swiped at the same time, as shown in FIG. 5. In this caseoutput data from the sensor 60 is logically split along two or morepaths for parallel processing in separate processors 62.

[0021] It will be understood that the processors 42, 52 or 62 may beused to perform all of the fingerprint analysis and correlationfunctions discussed with reference to FIG. 1. For each fingerprintcompared with previously stored reference fingerprint data, a separatepass/reject or match/no-match signal will be generated. These multipleresults may be combined in any desired way, such as by logically ANDingor logically ORing, depending on the level of security desired.

[0022] Although multiple processors are depicted at 42, 52 and 62, itwill be understood that a single processor of appropriate speed might beemployed in each instance. In other words, the parallel processingfunctions shown as being performed in multiple processors may beperformed with equivalent results in a single, higher speed processorperforming parallel processing with appropriate software, such as bymultitasking.

[0023] Any suitable fingerprint correlation algorithm may be used inconjunction with the present invention. For example the correlationtechnique disclosed in copending U.S. patent application Ser. No.09/995,330, filed Dec. 22, 1997, entitled “Fingerprint FeatureCorrelator,” may be employed to perform the necessary steps offingerprint analysis and correlation.

[0024] It will be apparent from the foregoing that the present inventionprovides a significant improvement over identity verification systems ofthe prior art. In summary, the invention provides higher accuracy,faster processing, lower sensor costs, more efficient use of devicespace, and simplicity of use.

[0025] Higher accuracy results from using at least twice as muchfingerprint information in a single verification operation. Fasterverification processing is obtained because multiple fingerprint sensorscan be easily coupled to multiple processors operating in parallel.Lower sensor costs follow from the use of small, readily availablesensors instead of larger customized sensors. Multiple sensors increasethe consumption of space only linearly, rather than in proportion to thesquare or cube of the sensor dimensions. For example, two sensors occupyonly twice as much space or volume as a single sensor, but doubling thesize of a sensor is likely to increase the space or volume consumed by afactor of four. Finally, a multiple-finger, multiple-scanner device isjust as easy to use as a single-finger, single-scanner device. From auser standpoint, the only difference is how many fingers the user mustplace in the scanning device.

[0026] Although the invention has been described in detail for purposesof illustration, it will be appreciated that various modifications couldbe made without departing from the spirit and scope of the invention.For example, although the invention has been described in termsapplicable to identity verification by fingerprint correlation, it willbe understood that the principles of the invention apply equally well toidentity verification using other biometric properties, such iris scansof two eyes using two scanners. Accordingly, the invention should not belimited except as by the accompanying claims.

What is claimed is:
 1. A method for performing biometric identityverification with improved accuracy, the method comprising the steps of:scanning at least two biometric features of a user simultaneously, usingat least two practically identical biometric scanners; processing datafrom the at least two scanners in at least one processor, to obtainbiometric data that uniquely identify the scanned biometric features;and comparing the biometric data with reference biometric data recordedfrom the user during an enrollment procedure, to verify the identity ofthe user; wherein simultaneous use of multiple biometric scannersprovides desirable improvements in accuracy and processing speed, at alower cost than by using a single, larger biometric scanner.
 2. A methodfor performing biometric identity verification with improved accuracy,the method comprising the steps of: scanning at least two biometricfeatures of a user simultaneously, using at least two practicallyidentical biometric scanners; processing data from the at least twoscanners, in at least two processors operating in parallel, to obtainbiometric data that uniquely identify the scanned biometric features;and comparing the biometric data with reference biometric data recordedfrom the user during an enrollment procedure, to verify the identity ofthe user; wherein simultaneous use of multiple biometric scannersprovides desirable improvements in accuracy and processing speed, at alower cost than by using a single, larger biometric scanner.
 3. A methodfor performing biometric identity verification with improved accuracy,the method comprising the steps of: scanning at least two fingerprintsof a user simultaneously, using at least two practically identicalbiometric scanners; processing data from the at least two scanners in atleast one processor, to obtain biometric data that uniquely identify thescanned biometric features; and comparing the biometric data withreference biometric data recorded from the user during an enrollmentprocedure, to verify the identity of the user; wherein simultaneous useof multiple biometric scanners provides desirable improvements inaccuracy and processing speed, at a lower cost than by using a single,larger biometric scanner.
 4. A method as defined in claim 3, wherein thestep of scanning at least two fingerprints includes scanning thefingerprints with at least two two-dimensional scanners.
 5. A method forperforming biometric identity verification with improved accuracy, themethod comprising the steps of: scanning at least two fingerprints of auser simultaneously, using at least two practically identicalone-dimensional scanners; processing data from the at least two scannersin at least one processor including converter one-dimensional scannerdata to two-dimensional fingerprint data, to obtain biometric data thatuniquely identify the scanned biometric features; and comparing thebiometric data with reference biometric data recorded from the userduring an enrollment procedure, to verify the identity of the user;wherein simultaneous use of multiple biometric scanners providesdesirable improvements in accuracy and processing speed, at a lower costthan by using a single, larger biometric scanner. scanners, and the stepof processing the data from the scanners includes convertingone-dimensional scanner data to two-dimensional fingerprint data.
 6. Amethod as defined in claim 5, wherein the step of scanning at least twofingerprints uses a single, logically segmented one-dimensional scanner.7. A system for performing biometric identity verification with improvedaccuracy, the system comprising: at least two practically identicalbiometric scanners, for scanning at least two biometric features of auser simultaneously; at least one processor, for processing data fromthe at least two scanners to obtain biometric data that uniquelyidentify the scanned biometric features; and comparison logic, forcomparing the biometric data with reference biometric data recorded fromthe user during an enrollment procedure, to verify the identity of theuser; wherein simultaneous use of multiple biometric scanners providesdesirable improvements in accuracy and processing speed, at a lower costthan by using a single, larger biometric scanner.
 8. A system as definedin claim 7, wherein the at least one processor includes at least twoprocessors operating in parallel.
 9. A system as defined in claim 7,wherein the scanners are fingerprint scanners, for scanning at least twofingerprints of the user simultaneously.
 10. A system as defined inclaim 9, wherein the fingerprint scanners are two-dimensional scanners.11. A system for performing biometric identity verification withimproved accuracy, the system comprising: at least two practicallyidentical one-dimensional fingerprint scanners, for scanning at leasttwo fingerprints of a user simultaneously; two processors ordinarily inparallel each including conversion logic, for processing data from theat least two scanners to obtain biometric data that uniquely identifythe scanned biometric features; including converting one-dimensionalscanner data to two-dimensional fingerprint data; and comparison logic,for comparing the biometric data with reference biometric data recordedfrom the user during an enrollment procedure, to verify the identity ofthe user; wherein simultaneous use of multiple biometric scannersprovides desirable improvements in accuracy and processing speed, at alower cost than by using a single, larger biometric scanner.
 12. Asystem for performing biometric identity verification with improvedaccuracy, the system comprising: at least two practically identicalone-dimensional fingerprint scanners combined to form a single logicallysegmented one-dimensional scanner, for scanning at least twofingerprints of a user simultaneously; two processors ordinarily inparallel each including conversion logic for processing data from the atleast two scanners to obtain biometric data that uniquely identify thescanned biometric features, including converting one-dimensional scannerdata to two-dimensional fingerprint data; and comparison logic, forcomparing the biometric data with reference biometric data recorded fromthe user during an enrollment procedure, to verify the identity of theuser; wherein simultaneous use of multiple biometric scanners providesdesirable improvements in accuracy and processing speed, at a lower costthan by using a single, larger biometric scanner.